On screen, Stephen Lang can be an awfully scary guy. A veteran of villainous muscleheads and hard-nosed military types, he's best known as Colonel Quaritch — that big, genocidal, buzz-topped security chief who terrorized the gentle blue bipeds of "Avatar."

But he's at peace with this. At 61, he's had decades of work and myriad roles spanning Broadway (as Happy Loman, Willy's son, in a 1984 "Death of a Salesman" revival) and tough indie drama (as Paddy, the sloshed and abusive longshoreman of "White Irish Drinkers"). So he knows a good gig when he sees one.

"If I get typecast at this point in my career as a tough old dude, I'm all right with that," he said. "It's better that than the ice cream man."

Chatting on the phone, Lang was everything his typecasting isn't: mindful, articulate, cultured, calm. The subject was "The Wheatfield," a hybrid program recognizing the 150th anniversary of the Battle of Gettysburg that's scheduled for 4 p.m. Sunday at Chatham's Crandell Theatre.

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At a glance

"The Wheatfield"

When: 4 p.m. Sunday, Dec. 15

Where: Crandell Theatre, 48 Main St.,Chatham.

Tickets: $15, or $10 for students and members of the Chatham Film Club and Columbia County Historial Society. Available at door.

The actor, who bought a house in Kinderhook several years ago with his wife, Tina, said the program evolved from "Beyond Glory," a one-man show that he adapted from Larry Smith's book highlighting Medal of Honor recipients. Lang performed the play off-Broadway in 2007 and has since taken it to military installations and theaters around the country, returning most recently from a tour with stops in Kentucky, Kansas, Wisconsin. In January he'll bring it to troops in the Middle East.

His latest work focuses on Gettysburg, which lasted the first three days of July 1863 and left around 50,000 dead, lost or wounded. "The Wheatfield" tells the tale of one man in one patch of it: James Jackson Purman, a Pennsylvania soldier who fought in that trapezoidal, 20-acre field of grain on the battle's long and brutal second day. The fighting at the Wheatfield "was some of the bloodiest fighting in the entire battle. It was really hand-to-hand stuff," Lang said, "and when the armies finally settled down for the night — when it finally stopped — there were a lot of men lying in the field."

Purman, still standing, stopped to aid a wounded comrade. "That delay proved his undoing. He was taken down at point-blank range. His leg was shattered by a confederate ball, and he lay there in that field all night. And then, next morning, when the sun rose on July 3 — it was very, very hot — he raised himself up to look around, and he was shot again."

Closer to the Confederate line than his own, Purman called out to the enemy for help. What happened next captured, with intimate human nuance, the vast forces that drove the Civil War and brought it to a close. "I love the story," Lang said. "Because, in its own way, it encapsulated the entire war."

He transformed Purman's saga into an 18-minute theater piece, supplementing it with photos and news reels of Gettysburg's 50th reunion. Recalling this footage, Lang unleashed a vivid description that he intended as prose but sounded like poetry:

"Old men from both sides ...

These old codgers

With their long beards

And their uniforms

And their gaunt figures dotted across the field

Waving their canes."

(And now take that, typecasting.)

"The Wheatfield" premiered at Gettysburg this past summer. At the Crandell, Lang's performance will be followed by a 10-minute short from identica-twin filmmakers Alexander and Adrian Smith, who digitally animated the theater piece. "I did some performance capture," Lang said. "So they were actually animating me."

Motion capture? Must have felt like he was back on the set of "Avatar." "Yes, absolutely," Lang agreed. "Except the catering wasn't as good."

Speaking of "Avatar," Lang just signed on for three sequels, never mind that Quaritch was drilled with arrows the last time we saw him. And that's about all the speaking of it he can do. "What I will be doing in them is just a matter of speculation and conjecture. The truth of the matter is, I will not see a script until after the first snow falls this year — and then the cone of silence will probably be descending," he said. "It's the cone of ignorance right now."

He's happy to spend more time as the heinous Col. Quaritch, one of the many muscled meanies crowding his resume. He doesn't mind. They're good company.

"I'm just an old ass-kicker. It is what it is," he said. "Just as long as I get a chance to do different spins on the ass-kicker — because there's more than one way to kick ass."